Meeting Abstract
Even though Unmanned Aerial Vehicles (UAVs) operating at low Reynolds numbers are becoming common, their performance and maneuverability are still greatly limited due to aerodynamic phenomena such as stall and flow separation. Birds mitigate those limitations by adapting their wings and feather shapes during flight. Equipped with a set of small feathers, known as Alula, located near the leading edge and covering 5% to 20% of the span, bird wings can sustain the lift necessary to fly at low velocities and high angles of attack. In this presentation, an alula-inspired leading edge device is installed on a high-lift airfoil and a moderate aspect ratio wing. Wind tunnel experiments are conducted at post-stall and deep-stall angles of attack and at Reynolds numbers of 100,000 and 135,000. Experimental results including integrated force measurements and hot-wire anemometry are presented. The presentation examines the distinctive effects of the geometric parameters of an alula-inspired leading-edge device (LEAD) on the aerodynamic performance of both the airfoil and the finite wing are discussed. Results show that the LEAD affects the airflow in two fundamental ways. First, it increases the capability of the wing to maintain higher pressure gradients by modifying the near-wall flow close to the leading-edge. Second, it generates tip vortices that modify the turbulence on the upper-surface of the wing, delaying flow separation. Post stall lift improvements of up to 32% are reported, confirming that the LEAD is a post stall and a three-dimensional device. Results show that these lift improvements are more sensitive to the LEAD relative angle of attack and root location than to the LEAD tip deflection angle.
